I. Field of the Invention
The technology disclosed herein relates to the sector of metal sections (typically made of aluminium) for forming window and door frames. In particular, it relates to an uninsulated section which is suitable for producing an insulated section used for the assembly of thermal break window and door frames. The technology disclosed herein also relates to a process for producing, from said uninsulated section, an insulated section for assembling thermal break window and door frames.
II. Related Art and Other Considerations
Various metal sections, which are typically made of aluminium, are known to be used in order to form frames for doors, windows or partitions. In particular, cold or uninsulated sections are known where metallic continuity exists between the section parts exposed to the external environment and the section parts inside a substantially closed environment (for example an apartment). Since aluminium is a good heat conductor, uninsulated sections therefore have the drawback that they allow heat exchange between the interior and exterior.
In order to overcome these drawbacks, for some time insulated sections suitable for forming “thermal break” window and door frames have been known. In thermal break window and door frames, the externally exposed aluminium part is separated from the internal part by means of heat-insulating bodies. A thermal break chamber with walls made of heat-insulating material is formed in these sections. Usually, this material is a plastic material. Typically, this plastic material is polyamide, ABS, PVC or the like. This chamber partially made of plastic material interrupts the transmission of heat by means of conduction between the outer part and inner part and provides the section with a high heat-insulating capacity.
The sections which are currently known for the formation of thermal break window and door frames are obtained by suitably assembling two sections or separate half-shells which are obtained by means of extrusion inside two separate extruders. The thermal break chamber is formed by inserting the end of two polyamide bars inside suitable cavities provided in the two half-shells of the section. Alternatively, heat-insulating bodies with a tubular shape are used. Each of the abovementioned special cavities is delimited by a pair of longitudinal teeth able to be bent or by a bendable longitudinal tooth and a fixed shoulder. During insertion of the bars or the tubular body, the teeth are all open in order to allow precisely easy insertion of the bars or the tubular body, respectively. After inserting the bars or the tubular body inside the respective cavities, the semi-finished section (comprising the two half-shells and the polyamide bars loose inside the respective cavities) is processed by a rolling machine. The rolling machine bends slightly the teeth of both cavities and ensures firm fastening together of the bars, or the tubular body, made of heat-insulating material and the half-shells.
This solution has the drawback that assembly is fairly laborious and difficult to automate completely. Even where it is automated, assembly results in long processing times owing to the need to carry out a lot of manual checks. The two separated half-shells must be moved close together to allow insertion of the polyamide bars inside the appropriate seats of both half-shells. They are then passed through a rolling machine which bends the teeth and fixes the polyamide bars in position. This laborious assembly process which cannot be completely automated results in high costs.
Another disadvantage of the abovementioned known solution is that associated with the machining tolerances. The problem arises from the fact that the two half-shells are typically extruded using two different extruders. During assembly the problem may arise of not managing to assemble the two half-shells (or of assembling them in an imperfect manner) if the tolerances of one or other half-shell are excessive. EP 0,653,541 discloses an uninsulated section which allows the production of an insulated section for thermal break window and door frames.
The section according to EP 0,653,541 eliminates some of the problems mentioned above. In particular, it is advantageous because it is obtained by extruding a single section from a single extruder or die. This allows the machining tolerances to be kept small.
However, assembly of the section according to EP 0,653,541 is also difficult to automate completely. In fact, firstly it is necessary to insert the heat-insulating elements in the appropriate seats. Then, using at least two different tools, the walls 9 which connect the inner half-shell to the outer half-shell are cut. This operation is long and results in a not insignificant amount of waste material. Moreover, the cutting step must be performed in a very precise manner in order to avoid damaging the teeth 11 and the parts made of heat-insulating material. Another drawback consists in the impossibility of knurling the bottom of the cavities which house the heat-insulating elements and therefore the adhesion is not perfect. A further drawback consists in the impossibility of using heat-insulating elements of different forms and sizes. In other words, it is not possible to use longer heat-insulating elements which space by a greater amount the inner half-shell from the outer half-shell.